Locking screw



FIG. 1 is a perspective view of a locking screw showing my new design.

FIG. 2 is a top view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a front view thereof; and

FIG. 5 is a bottom view thereof. 

The ornamental design for a locking screw, as shown and described. 